A wide variety of machine systems utilize friction elements such as friction discs for transferring energy between machine components. Torque converters, clutches, brakes and various other machine systems, for example, employ friction discs to provide a rotational coupling or frictional energy transfer between components in a machine system. Slipping of the friction element will cause wearing down of the friction material over time. After a certain degree of wear, the friction elements typically need to be replaced, or the machine system of which they are a part needs to be replaced.
It is common for a machine system employing such friction elements to be serviced, remanufactured or replaced prior to at least some of its constituent friction elements reaching a degree of wear that renders them unsuitable. In other words, machine systems such as transmissions, clutches, brakes, etc. may be sent for service or remanufacturing because part of the system is worn or not functioning properly, while the friction elements themselves remain functionable and are not overly worn. Nevertheless, the friction elements are typically replaced with new friction elements during such servicing or remanufacturing. This is done because it has heretofore been difficult to verify with a high degree of certainty that the friction elements are in good condition. Thus, all the used friction elements are typically scrapped and replaced with new friction elements to ensure that only good functioning friction elements are included in the repaired or remanufactured system.
While the cost of an individual friction element will often be fairly low, the relatively large numbers of friction discs used in certain machine systems such as transmissions and clutches renders a 100% scrapping approach highly inefficient and economically wasteful.
The economic disincentive to scrapping otherwise suitable used friction discs has been recognized for some time. With regard to friction discs known in the art as “low energy” friction discs, remanufacturers have recognized that the color of the friction material can indicate its suitability for further service. Other friction elements, in particular “high energy” friction discs, often a composite of Kevlar™, paper and the like employed in a lubricated environment, cannot indicate their suitability for further use by their color due to their unique material properties and design characteristics. According to some estimates, at least 50% of used high energy friction elements might actually be suitable for returning to service in a machine system. But because the techniques for quickly and consistently verifying their suitability have not heretofore been available, all are typically scrapped.